Method and machine for cutting gears



May 27, 1952 E. WILDHABER 2,598,327

METHOD AND MACHINE FOR CUTTING GEARS Filed June 19, 1946 3 Sheets-Sheet 1 FIG. 3

ERNEST W ILDHABER INVEN TOR.

BY Attemey y 1952 E. WILDHABER 2,598,327

METHOD AND MACHINE FOR CUTTING GEARS Filed June 19, 1946 3 Sheets-Sheet 2 M ERNEST WILDHABER INVEN TOR.

BY Akin-n15 j y 27, 1952 E. WILDHABER ,327

METHOD AND MACHINE FOR CUTTING GEARS Filed June 19, 1946 3 Sheets-Sheet 3 FIG. l4

ERNEST WILDHABER INVENTOR.

BY 4 z 2 Atterne Patented May 27, 1952 UNITED METHOD AND MACHINE FOR CUT-TING at e GEARS Ernes W hah V l l The present invention relates to tapered. gears d pa tic larly to the prqduct' oi tar eted gears which are to .mesh with their ages inclined to one another at an angle of less than thirty degrees.

Tapered gears are ordinarily generated with c p oc t plan n oo s, 01' w th lie e-mil e s milar ear cutters in a e e a in o eratiqn in which the tool represents a crown gear .or

other tapered basic ear, and in wh ch the tea and work are rolled relative to .0116 .anqther as ou h the ar being cu vwere r lling an th basic gear represented by the tool Fitlo rir duce tapered gears which are to mesh with a Small B lm, e s si g 9 Kiiichestci," NIY'.;"a corporation P esen i r ta a ei a tea 9 y. ld i9% gear form trererably QlOt'ed. t t extending" in the 'i 9 i 'inar v 1 i ,t a at iiiti i a is. f 't nventign, the jt'ool f;re1 ivetetheiwerrt at its axis intrsect's"the f t e workland ispreferably inclined tothefwork axis' at'the pitch a gle of shaft angle, bevel orzhypoidlgearge ler t il chines are ordinarily required which are altogether out of proportion in size to the ,size of the gears to be .cut. While lmethodsef cutting tapered gears .Of small shaft an le 9 .maahine of size proportionate .to the ,size .of the ear fv have been devised, these methods involve some complications.

A primary object .of the invention ,is to provide a simple method for generating itaQenQ gears of small .shaftangle.whichmay-belpracticed on a machine proportional in size to .the gears to .be produced;

.Another object of the invention is to provide a method for correctly cutting-tapered,gearsjof small shaft .angle with a tool of gear iorm.

A further object of the inventitm is to provide a method for cutting Iaiieredgears of small shaft angles with a tool of 'gear rerm in which the tool used is'difierent from the mating gear of the gear which is beingcut.

Still another object of the invention is to provide a method .for cuttingepair oftapered gears of small shaft angle with tools of gear form, which will permit ,of using .tools ,of the "same tooth number inth generatioii oi gpth inertibers of the pair. M M

A u h b ected the rei e i t nrq is a methodfor cui ine a eieegeared Shaft angle with tools of gear form-lby whi h sui ble localizatibn o tqgt heari l v b obtained w en a hai 9 ea -5 s enrbduped ar in mesh. V

.A still fur her vab ec p the Jnreniie i t p v e an i p oved qiq m p a v cuttin machine -for cutting tapered gears ,yv ith tools of gear form.

Other objects of the tinyrentiqn. will 13a apparent hereinafter from the specification and f rgrn there itallef the a p nd dl laim In cutting a ,rtape ed g ar assumin =.t9 the .tha lthe aae ao th ite a ifi .l a th same lnlane but are afieii arl fiis psfi i and .a se :fmm emt e Wit thi raneement titlis poss ble to. t e amount .o tooth hearing or contact -.hetween the matin tooth surfaces of the mating gears by changing the an'l'ount'i'of loffsetnof work and tool axes;

" In'-the';l rawings":

1 a diagrammatic view showing alpair 2 ate e d e H ngle proa cutting stroke from the small to the large end of the teeth;

Fig. 5 is a diagrammatic view taken in the common pitch plane of the mating gears, and illustrating certain relationships between the gears;

Fig. 6 is a similar diagrammatic view showing the lines of mesh of one of the gears in the pitch plane;

Fig. '7 is a similar diagrammatic View showing the lines of mesh of both gears in the pitch plane;

Figs. 8 and 9 are diagrammatic views at right angles to one another, illustrating a modification of the invention;

Fig. 10 is a diagrammatic View, similar to Fig. 9, illustrating a further modification of the invention;

Figs. 11 and 12 are diagrammatic views taken in the same directions as Figs. 9 and 8, respectively, and illustrating certain relationshipsunderlying the invention;

Fig. 13 is an enlarged diagrammatic view, showing one of the gear teeth, and taken along the tangent to the tooth shown in Fig. 11; and

Fig. 14 is a diagrammatic view showing a tapered gear cutting machine built according to one embodiment of this invention.

Referring now to the drawings, and 2| denote, respectively, the two members of a pair of angular bevel gears produced according to one embodiment of this invention. The axes of these gears are desingated 22 and 23, respectively. The gears have pitch angles g and G, respectively, and mesh along an instantaneous axis I which intersects axes 22 and 23 of the gears in the common apex 25 of the gears.

As will be seen, the distance from the cone apex 25 of the gears to a mean point P along the length of a tooth of either gear is quite long, as compared with the length of the gear teeth. To generate these gears by any standard method of generating bevel gears, the gears would have to be rolled during the generating process about the axis of a basic crown gear or other basic gear whose axis passes through the cone apex 25. Hence, by any ordinary method of generating bevel gears, a machine of very large size, as compared with the size of the gears themselves, would be required.

In accordance with the present invention, both gears 20 and 2| may be generated with'cutters which are of gear shape and which have a plua gear-shaped cutter whose axis 32 is parallel to the instantaneous axis I of mesh of the gears and intersects the gear axis 22 in a point 35 beyond the cone apex 25. The cutter is reciprocated along its axis in a straight path when the cutter has straight teeth, but if a cutter having helical teeth is employed, then the cutter is reciprocated in a helical path about its axis, as indicated by the arrow 33, the direction of which corresponds to the direction required for a pinion 20 having right-hand teeth. Usually, it is preferred to use a helical tool.

In this embodiment of the invention, the gear 2| is produced in a similar manner, as shown in Fig. 3. If cutters of helical form are employed. then a cutter 30' is used in cutting gear 2| which is of opposite hand from the hand of the cutter 3|! and is reciprocated in the opposite helical direction as indicated by the arrow 33'. Preferably, the cutter 36 has the same number of teeth as the cutter 3|]. It's axis 32' is again positioned parallel to the instantaneous axis I and intersects the gear axis 23 in a point 35 beyond the cone apex 25.

Both members 20 and 2| of the gear pair are generated. As the cutter reciprocates across the face of either gear, the cutter and gear are rotated about their respective axes to efiect the generating motion. In its straight or helical reciprocating motion, the cutter describes a straight spur gear or a helical gear, respectively, and the cutting motion combined with the generating rotation of cutter and work, causes the cutter to produce a gear 2 or 2| conjugate to the spur or helical gear described by the cutter.

The tooth shapes produced on the gears will now be analyzed. The spur or helical gear described by the cutter 30 meshes with the work 22 e in the manner of two meshing bevel gears inasmuch as the two axes 32 and 22 intersect at 35. When their pitch surfaces roll without sliding at mean point-P, then the straight line P--35 is the instantaneous axis of relative motion of the gear 20 being cut and the cylindrical gear described by the cutter. The surface of action of this mesh contains the instantaneous axis P35, and at all points of this instantaneous axis is tangent to the tooth normal of the given spur or helical gear erected in the position of contact at said points. Moreover, if the cutter is so constructed as to describe an involute spur or helical gear, this surface contains all tooth normals which are tangent distance 3537 T r-tan 9 tan -distance P37 A r A-tan g+r tan g Likewise on the gear 2| r-tan G *m+ In this last equation, r refers to the gear described by cutter 30'.

Figs. 2 and 3 show the cutters cutting the teeth of the work on cutting strokeswhich extend from the small or inner end of the teeth to the outer or larger end thereof. It is also possible with the present invention to cut the teeth from the large or outer end thereof to the'small or inner end thereof. This is illustrated in Fig. 4 where the same cutter 39 may be employed as in Fig. 2 to cut the pinion 28, but where the cutter operates from the outer or large end 0 of the pinion teeth toward the inner or smaller end i of the teeth. The same relationships and formulas exist in either case.

Fig. 5 is a view of the pitch plane of mesh of the gears, that is, of the plane containing the in- "apogee? stantaneous axis I and tangent to the pitchsurfaces of the two gears. This plane is perpendicular to the drawing plane of Fig. 2 and in Fig. 5 is viewed from the right of Fig. 2. A point P is considered along the instantaneous axis 38 of out, which is displaced from the mean contact point P. This point P projects to the pitch plane 27 as a point P". Both of these points project into the same point P in Fig. 5. Let dis tance PP" be an infinitesimal distance dA. The distance PP" of point P from the pitch plane is then:

dA-tan (-dg).

P" being that much below the plane of Fig. 5.

For further analysis, helical teeth will be considered since helical teeth are mathematically a more general form of tooth. The formu'lasfor straight teeth can be obtained .from the formulas for helical teeth simply 'by making the helix angle 8 equal zero. The tooth tangent t at point P is inclined at the helix angle 'or spiral angle s to the instantaneous axis I (Fig. 5). '29 indicates the tooth normal at point 'P. Inasmuch as the point P is assumed at an infinitesimal distance from point P, the direction of the tooth normal at point P differs only infinitesimally from the direction of the tooth normal at point'P. The

tooth normal at point P intersects the pitchplane at a point Q for one side of the teeth and b at a point Q on the other side of the teeth.

The pressure angle p at point P is the inclination of the tooth normal to the pitch plane and is preferably made numerically equal on both sides of the teeth. For one side of a tooth, it'will be considered as a positive quantity, however, and for the opposite side as a negative quantity, indicating the opposite directions of inclination of the opposite sides of the teeth. The inclination of the normal PQ will hereinafter be considered as a positive quantity and the inclination of the normal PQ' as a negative quantity. Distances PQ and P--Q', as projected in Fig. 5, are then:

PIP/I tan p tan (dg) dA tan :1)

Point Q of the pinion will mesh with the gear 2! in a different position from its point of mesh with the generating gear 'represented by cutter 3%, namely, when turned back about the pinion axis 22 to the instantaneous axisl. ".The turning angle about the pinion .axis is then:

distance PQ-cos s 6 inion axis can be resolved into a component about an axis perpendicular to the'pi-tch plane:

I-sin g dp;

and intoa component ,dp' about the instantaneous axis I; V

Inasmuch as the instantaneous axis I and the cutter axis 32 are parallel, the eifect of the latter component adds directly to 11m, and since:

cos 9 =A-tan y we have:

The resultant angle dp" amounts, therefore, to:

the other component amounts .to

pitch plane, ,it gives an increase in spiral angle of:

inasmuch as. the infinitesimal turning motion dp" about the instantaneous axis I can be resolved into a turning motion about the tooth tangent t (Fig. 5) and into a turning motion:

dA cos s 4 I 1 tan p A tan g+r Ts'tan'pll The considered point .Q has a distance dA' lengthwise of instantaneous axial as .follows:

dA =dA+distance P Q-sin "s T .d a s1ns rtan g 1 R17 This infinitesimal turning motion about the '70 Hence, also:

"dA cos s r tan 9 A tan sin s 1 tan g 1 [A tan g+r Y p tan 1) (A tan g-l-r) This equation is also applicable to the oppoof the pitch lines: site side of the teeth when pressure angle 12 is 1 introduced there as a negative quantity.

I Fig. 6 shows the pitch plane and the lines of T D mesh P-Q1 and PQ2 of the gear 2| in that 5 and plane with the cylindrical gear represented by tool 30'. Fig. 7 is a further view of the pitch D= 8 plane with the pinion 2B assumed below the pitch plane and the gear 22 above it in mesh with hence:

I 1 [i i 1' A tan g r A tan G l (cos s) 1 r A tanp[ +sins rtang sins rtanG tan p A tan g+r tan p (A tan G-l-r) the pinion 20. The lines of mesh along which It is to be observed that in the factors below contact takes place between each of the two the division line in the last equation the second members and 2| and the respective cylindrical 20 members are small quantities as compared with gears represented by the reciprocating cutters the first member which equals unity. This is and 30 are here superimposed. Line PQ partly due to the presence of tangent g or tanis the line of mesh of the pinion 2D and its gengent G which are small quantities at the small erating gear as above explained on one side of shaft angles between the mating gears conthe teeth. Line PQ1 is the corresponding line of 25 sidered. Moreover, the second members have mesh on the same side of the teeth between the opposite algebraic signs. The product of the gear 2| and its generating gear. On this side two factors difiers, therefore, very little from the pressure angle 10 is introduced as a positive unity and a good and suflicient approximation quantity into the gear formulas given below. of the relative curvature With the procedure outlined for the pinion, 3

the folhwing equation y be derived for the 1 ear 2!: P

cos 8 i 1 tan G 1/ I 1 tan [112% LSm S tan (A an 0+?) p tan 7) (A tan G+r) The difference (ds"ds1") will be used to deteris obtained by neglecting its slight difference mine the ease-01f of the tooth bearing at the from unity. ends of mating teeth:

dA cos s /r II (d8 Atan sins rtang sins rtanG p tan p (A tan g-l-r) tan p (A tan G-l-r) rtang sins rtanG I rtanG' I sins rtang (A tan g-i-rfl tan p (A tan G+T)}T(A tan G+r)1 tan p (A tan g+r)} sin 8 r tan G sin a 1* tan g m (A tan G+r)} s'tan tan p (A tan g+r)}] sin s-tan p{1 The quantity in the bracket in the above formula can be written as: The ease-off Z at the tooth ends of the pitch rtang rtanG cos s 1 1 (At-an +1 (1 (AtanG+1-) (1 Sm 8) A [1 1 1 r A tang r A tanG Let D denote the infinitesimal distance of the lines can thus be computed approximately for considered pitch point Q from the mean pitch gears of a face width F as follows: point P measured in the direction of the tooth 1 F 2 tangent so that: Z

21* 2 cos s dA'=D-cos s 2 At a point, which is a distance D away from Z 1 /F cos 8 I: 1 1 1 1 the pitch point P, there is a difference 8 tan A 1 1 s e separa ion 0 e ma 1n pi c mes spiral t f of h mgtmg tooth sldes' Tms at the tooth ends. It is measured in opposite dlfierence 1S m dlrectmn to produce easeofi directions on the two sides of the teeth as indithe tooth bearing at the tooth ends on 9 cated by the algebraic sign and amounts to an sides of the teeth and corresponds to a relative easewfi on both sides of the teeth.

curvature The formula indicates that the ease-oil is re- 1 duced by introducing a spiral angle s, increasingly so with increasing spiral angle.

Gears produced according to the present invention are far less subject to undercut. at the small ends of the teeth and to pointed tooth tops at the large end than are gears, of pairs composed of a cylindrical gear and a tapered gear which mesh at the same shaft angle as, gears made according to the present invention. Moreover, the gears of the present invention have localized tooth bearing. Furthermore, standard cutters can be employed in cutting gears according to the present. invention, whereas on ratios of nearly 1 to 1 and, more generally, with large sized pinions, an unduly large cutter has to be employed where the cutter corresponds to the mating pinion. Also,

with the present invention, there is less profile sliding at the ends of the teeth inasmuch as the teeth extend in the general direction of the instantaneous axis.

To use standard cutter diameters, it is, of course, necessary that a standard pitch be used in the gear design at mean point P. If Pd denotes a standard diametral pitch, the mean gear diameters (2Rp:2A sin g) and 2R:2A sin G and the tooth numbers n and N, respectively of the gears should fulfill the equations:

3L Ni d and where Hp and R are the pitch radii of mating pinion and gear, respectively.

In the embodiment of the invention just described, control over the amount of ease-off of the tooth bearing at the tooth ends is limited. A

' modification of the invention will now be described through which the ease-off of the bearing at the tooth ends is under more complete control. This modification is illustrated in Figs. 8 to 14 inclusive.

Here the axis of the cutter and the axis of the work are no longer in the same plane. The cutter has its axis 41 inclined to and offset from the axis 22' of the pinion or gear 20' being out. As the cutter reciprocates, it describes a cylindrical gear 40 whose axis M is inclined to the pitch cone element extending through mean point P of gear 20' and whose cylindrical surface is tangent at P to th conical pitch surface of the gear 2c. The inclination of the cutter axis is denoted 6 (Fig. 9) To obtain gear contact at-point P, the normal displacement along the tooth normal b at point P should be equal on gear 20' and the gear i upon corresponding rotation of the gears.

The peripheral displacement per rotation through a tooth is:

A sin g on gear 26' and:

on the gear Atrepresented by the cutter, where n represents the number of teeth in gear! or .he cutter. The corresponding normal displacement is a product of the above displacement multiplied by the cosine of the respective spiral angles. Let Sc denote the spiral angle or helix angle of the gear 40 represented by the cutter. The spiral angle s at point P of the gear 20' is then:

- cos (s +e)=2 cos 3,

A sin g A sin G cos 8,,

n N in cos (s l-.2)

This equation simply expresses the requirement that the normal circular pitch should be the same on the cutter and on both members of the bevel gear pair to be produced.

In cutting a gear according to this second embodiment of the invention, the same motions may be employed as in the first described modification of the invention. The only difference is that in the second embodiment the'cutter axis is ofiset from the work axis. The cutter is rec'iprocated along its axis 4|. It performs a straight or helical reciprocation, depending upon whether it should describe in its path a cylindrical gear with straight teeth or one with'helical teeth. In addition, a generating motion is provided which consists of rotation of the cutter on its axis and of the work on its axis. These generating motions are very slow and may be intermittent after each cutting stroke. They are as if the cylindrical gear represented by the reciprocating cutter were meshing with the gear which is being produced. It should be noted that no lateral feed motion is employed and that therefore the gear produced is directly and fully conjugate to the cylindrical gear represented by the tool. It can mesh with line contact with said gear.

At the end of each cutting stroke, the tool and work are, of course, separated slightly so that the tool clears the work during the return stroke.

The cylindrical pitch surface of the gear so represented by the cutter, shown in Figs. 8 and 9, contacts the conical pitch surface of the bevel gear 211' at point P only and is separated therefrom at all other points. When rotated bodily about the pinion axis 22' this cylindrical pitch surface envelops and describes a surfaceof revolution of concave axial shape. The profile of this surface is shown in dotted lines in Fig. 8 at 42. Its radius of curvature at point P is denoted at 43 in Fig. 3 and its center at Qx. The separation of this profile A! from its tangent at P indicates the amount by which the cutter will cut shallower at the point considered as compared with a cutter whose axis intersects the axis of the work. The latter cutterproduces an ease-off Z at the tooth endsas previously determined which may be in excess of the desired ease-off Z. The ease-off Z should, therefore, be reduced by a (ZZ'). This may require cutting shallow at the tooth ends of a total of on both members of the pair. In other Words, we could aim at a total curvature Curvature radius Tx depends largely on the inclination e. For itsadetermination, the normal at '45 in Fig. 9 is perpendicular to axis 4| and intersects it at Q; and it intersects axis 22' at Q. It intersects the plane P at point Q". This plane contains the pitch surface normal P--P1 (Fig. 8) and is perpendicular to the axial gear plane containing point P. The center of curvature Qx of the dotted axial profile 42 is attained by turning normal 45 and its point Q" about the gear axis into the axial plane from Q" to Q; on the pitch surface normal. In this turning motion, point Q" moves in a direction parallel to the drawing plane of Fig. 9, as long as infinitesimal distances PQ are considered. The distance PQK (Fig. 8) is therefore equal to the vertical elevation (Fig. 9) of point Q" from P.

In the projection of Fig. 9:

From Fig. 8:'

i s=P P+PP =A tan g+r aQz Qz a= 'z Hence on the gear 20':

On the mating gear 2!, pitch angle G is used instead of g, and:

21 sin e sin e r, A tan g-cos e-l-r A tan G- cos e+r gives the total curvature of the axial profiles of the mating gears when the same angular settings e and the same cutter radius r is used on both gears.

is found to be intermediate the values:

1 l 2 tan ll A tan g+r A tan G-l-r] and may be assumed approximately equal to the latter value. Thus:

tan cl: 1 1

A tan g+r A tan G+r ,F tan 3) 12 An initialtan e and e may be determined from this equation.

It is possible, also, to make an exact determination of the ease-off obtained with a given angular setting 6 and cutter radius r. First, the surface of action during generation of each gear is determined, that is, its tangent plane at mean point P. In Fig. 11, the tooth tangent t at point P shows the tooth direction. I) is the tooth normal at P. In the mesh between the gear 20' and the gear 40 represented by the cutter, point P of the gear 20' moves in a peripheral direction PS; and point P of the gear 40 represented by the cutter in the peripheral direction PS1 which includes the angle e with the direction PS. PS and PS1 represent the corresponding distances traveled. As seen, the end positions S and 51 are on a line SS1 parallel to the tooth tangent or pitch line tangent t.

Inasmuch as the gear 49, which is represented by the cutter, may contain either straight or helical teeth, it can be moved axially without altering the mesh and the surface of action. Thus, the gear 40 of Fig. 9 may be given a helical motion lengthwise of the teeth to move point S1 to S so that, in the resultant motion, point P of the gear 40 moves to S instead of moving to S1. The additional motion is made up of a turning motion Si-S' and of an axial motion S'S. The resulting or total turning motion of the helical gear 40 represented by the tool then compares with its turning motion without axial displacement as distance PS compares with the distance PS1.

Let wi denote the resultant angular velocity of the helical gear about its axis M, and let w and w denote, respectively, the angular velocities about the axis 22 and about the axis of the basic gear employed in generation of the gear which is to mate with gear 20. Distances PS and PS can then represent the velocities at pitch point P as follows:

PS=w A sin g=w" A sin G PS'=wr=w'A sin g-cos e Hence:

-cos c Inasmuch as with the added helical motion, point P of the helical gear moves in the same direction and at the same rate PS as point P of the gear 20, the relative motion can only be a turning motion about an instantaneous axis passing through P, and true rolling motion takes place at P. The instantaneous axis of this rolling motion can be obtained in known manner as follows. The individual angular velocities w and 201 are geometrically added to give the resultant relative angular velocity about the instantaneous axis in the direction of the instantaneous axis. Thus, angular velocity 1121 can be plotted as a distance PL in Figs. 11 and 12 drawn through P parallel to axis 41. Angular velocity w is then plotted at the same scale as a distance LM on a line drawn through L, parallel to axis 22' of gear 20'. Distance PM then determines the resultant relative angular velocity, and the line PM is the instantaneous axis. The surface of action contains the instantaneous axis and it either contains or is tangent to the tooth normal at P. Its tangent plane at P is, therefore, the plane connecting the instantaneous axis and the tooth normal at P.

There is a surface of action for each of the two sides of the teeth. Its tangent plane inter- 13 sects tli pitch plane, which is plane PSSi a line PM1 on one side of the gear teeth, arid in s line PMz on the other side. M11 and are obtained by drawing lines MMI and MMz through parallel to the two tooth surface normals at P, and by determining their intersection with the pitch plane. Lines PM; and PMZ represent the tangents at P to the lines of Iries'h in the pitch plane between the gear 20' and the generating ge'ar iii represented by the tool. After these are determined forboth tapered gears, the following equationslinay be derived by employing th pfii'ifiipls previousl diScldsdI s1n sczcoss sin e-cos e sin s-cos s T be introduced as a positive quantity on oiie side of the teeth and as a negative quantity on the opposite side. Mating tooth sides correspond to pressureanglesof the same algebraic sign.

A positive quantity Z indicates a separation or ease-off oii theside where the pressure angle p is positive; On the opposite side, where p is negative, Z appears negative if an ease-off. An algehrai'c sign opposite to the one indicated would show that the t'et'hhave too much stockat their ends, that is, a negative ease-off, which, of course, should be avoided. To obtain more ease-off, e should be reduced. Less ease-off is attained by increasing e. I

Preferably cutters 6f equal pitch diameter are used on both members of the tapered gear pair. lfreferably, also, the lead of the gear described by the cutter is selected equal in producing the two tapered gears. The hand, of course, is oppo- Sit.

m thissecon'd described embodiment or the invention it is pcssible to obtain a spiral angle "on the gear teeth with the cutter having straight teeth which represents spur gear. This modimatron is indicated in Fig. 10 'whe'rethe tooth normal b is shown perpendicular to theputter are H. Herethe butter represents a basic generating gear it t at has straight, spur teeth. cutting and generating motions are as in the previously described embodiments of the inventioii.

While the "invention has bee described in cbmieetien withthe production of tapered gears which have their axes intersecting, it is to be understood that it is applicable, also, to the production of tapered gears having ofise't axes'.

In Fig. I ha illustrated diagrammatically oile form of a filafih iil which may be Gilli 1?)Yed for practicing the present 'ihv'entibh. Here 50 centres the ase or frame or the machine and 51 an upright 6r dolumh that is s'eeured to the This lihe and; which in 'i'act,- inay be made integral therewith; Mounted upon the base for" redtmfiear adjustment thereon, is a table or slide 52'; and fnuhted in the table or slider: for angular adjustment therein about an axis 53 is a cradle 53.- The wdrk spindle 55 of the machine is journaled in the cradle, and the gear W, which is to be cut, is secured to the work spindle in any suitable manner. The axis of the work spindle, which is the axis of the gear, is denoted at 56.

Pivotally mounted upon the column 5| for angular adjustmentthereon about an axis is a swingable support 62. This support is guided in its angular adjustment by an arcuate guide surface 63 which is formed on the topof column 5| and which engages a complementary surface can the swingable support 62. The cutting tool T is secured to the cutter spindle 65 which is journaled in the cutter head 61 that is mounted on the support 62 for rectilinear adjustment thereon. The axis of the cutter spindleis denoted at 66. It intersects axis 60 in point 68. The head 61 is adjustable on the support 62 in the direction of the cutter axis 66.

The ineans for rotating the cutter and for effeting its reciprocating axial motion, and the means for relieving the cutter at the ends of its cutting "strokes maybe the same as employed in conventional type machines for cuttingspur and helical gears. The train of gearin for timing the rotary motion of the cutter and of the work about their respective axes 66 and 56 may be similar to the gear train employed in conventidnal type spur and helical gear cutting machines. Preferably, however, the timing train will contain a gear coaxial with cradle axis 53 and a gear coaxial with axis 60.

After resharpening, a conventional gearshaped cutter decreases in its diameter. An adjustment of its position is then required principally in a direction to inove the work and cutter relatively toward one another, that is, in the direction of the axis 60 (Fig. 14). This is accomplished by adjusting the slide 52 on the base 50. Other required compensatory readjustments are about the cradle axis 53 to slightly change the tilt of the Work axis 56 and 'abeut ax'isto. The amount of this last named readjustment is slight but important and depends en the helix angle of the generating gear represented by the cutter. The nature and amount or the required adjustment is readily determined on the testing machine by testing a gear but with a particular Setting against a master gear or with its mate. The adjustment-s provi ed on the machine of the present invennon a e also useful for other cutting changes as, for instance ror modifying the tooth shape to alibi? for ahticipat'ed distortions in the hardenmg.

1nsteae 6f angular adjustment about axis El), a lateral adjustment between the axes 66 and 55 may be provided, that is, ah adjustment in a "dii'ctif perpendicular to the drawing plane of Fig. 14 to bffset these a xe's net-n one another. ai' adj'u-s'tineht then takes the place of adjustment about pivot 60 which also ofisets the two axes. The same relative poer the two axes may be arrived at with faith 'ee strucuon,

re the invention has been described particularly cohn'eigtioii with the cutting of tabe er gears bffsinafl s'hfaft angle with cutters of eyiinerifcairgear fo -in, it may also e applied to the production of tapered gears with cylindrical and, if e is equal to e, that is, if the tilt is opposite, from that shown, then:

angle e is preferably kept larger than 30.

These formulas apply also to bobbing in which only depthwise feed is used, and no feed along the pitch cone element, nor any lateral feed is employed. However, if desired, helical feed along the hob axis can be used in place of depthwise feed. Such helical feed is known for hobbing worm wheels and will produce the same tooth shape as the depthwise feed when the final tooth shape is applied in the final position of feed.

While several different embodiments of the invention have been described, it is to be understood that the invention is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention, following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. The method of producing a pair of tapered gears which comprises cutting each member of the pair with a rotary tool of cylindrical gear shape by positioning said tool in engagement with the work with the axis of the tool parallel to the instantaneous axis of mesh of the pair of gears, and with the axis of the tool intersecting the axis of the work and reciprocating the tool in engagement with a tapered gear blank while rotating the tool and blank on their respective axes as though the blank were meshing with a cylindrical gear described by the cutting edges of the reciprocating tool, and whose axis intersects the axis of the blank.

2. The method of producing a pair of tapered gears which comprises cutting each member of the pair with a rotary tool of gear shape by reciprocating the tool in engagement with a tapered gear blank while rotating the tool and blank on their respective axes as though the blank were meshing with a cylindrical gear described by the reciprocating tool and whose axis intersects the axis of the blank in a point beyond the pitch cone apex of the blank.

3. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear other than its mate by positioning a rotary tool of cylindrical gear form in engagement with a tapered gear blank with its axis parallel to the instantaneous axis of mesh of the gear pair, and reciprocating saidtool axially while rotating the tool and blank about their respective axes as though the gear being out were meshing with a cylindrical gear described by the tool in its reciprooatory movement, the axis of the tool in- '16 tersecting the axis of the work, and the tools used in cutting the two members of the pair having equal numbers of teeth.

4. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear by axially reciprocating a rotary tool of cylindrical gear form in engagement with a gear blank while rotating the tool and blank about their respective axes as though the gear being out were meshing with a cylindrical gear described by the tool in its reciprocating movement, the axis of the tool intersecting the axis of the work and being inclined to the axis of the work at the pitch angle of the work, and the tools used in cutting the two members of the pair having equal numbers of teeth.

5. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear other than its mate by axially reciprocating a rotary tool of cylindrical gear form in engagement with a gear blank while rotating the tool and blank about their respective axes as though the gear being out were meshing with a cylindrical gear described by the tool in its reciprocating movement, the axis of the tool intersecting the axis of the work, the diameters of the two tools used in cutting the two members of the tapered gear pair being different so as to provide ease-off of the tooth hearing at the ends of the teeth on mating tooth surfaces of the pair of gears.

6. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear other than its mate by positioning a rotary tool of cylindrical gear form having helically arranged cutting teeth in engagement with a tapered gear blank so that the axis of the tool intersects the axis of the blank in a point beyond the pitch cone apex of the blank, and imparting helical reciprocating movements to the tool about and along its axis while efiecting a relative generating motion between the tool and the blank as though the gear being out were meshing with a helical gear described by the tool in its reciprocating movements, the tools used in cutting the two members of the tapered gear pair being of opposite hand and being given helical reciprocatory movements of opposite hand, and having equal numbers of teeth.

'7. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear other than its mate by positioning a rotary tool of cylindrical gear form having helically arranged cutting teeth in engagement with a tapered gear blank so that the axis of the tool intersects the axis of the blank in a point beyond the pitch cone apex of the blank, and imparting helical reciprocating movements to the tool about and along its axis while effecting a relative generating motion between the tool and blank as though the gear being out were meshing with the helical gear described by the tool in its reciprocating movement, the tools used in cutting the two members of the tapered gear pair being of opposite hand and being given helical reciprocating movements of opposite hand, and the helix angles of the two tools being selected so as to produce a suitable amount of localization of tooth bearing on the mating tooth surfaces of the tapered gear pair when in mesh.

8. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear other han it ma e y iien es r y tea -c ylindrical. ar. fo m ha in he ic ran ed uttin eeth n en a em n ith a tapered a blank sotl' at the aigis oilt h e tool intersects the axis; of "the blank in a point beyond thepitch 9 1 112 i he lanks and imparting helical reciprocating movements to the tool about and along its axis while efiecting a relative generating motion between the toolandrblank as though the gear being out were meshing with-the helical gear described: by the tool in its reciprocating movement, the tools used in cutting the two members of the tapered gear pair being of opposite hand and being given helical reciprocating movements of opposite hand, and the helix angles and diameters of the two tools being selected so as to produce a suitable amount of localization of tooth bearing on the mating tooth surfaces of the tapered gear pair when in mesh.

9. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear by positioning a tool of cylindrical gear form in engagement with a tapered gear blank with the axis of the tool inclined to but offset from the axis of the blank, and imparting axial reciprocating movements to the tool while effecting a relative generating movement between the tool and blank as though the gear being out were meshing with the cylindrical gear described by the tool in its reciprocating movements.

10. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear by positioning a tool of cylindrical gear form in engagement with a tapered gear blank with the axis of the tool inclined to but offset from the axis of the blank, and imparting axial reciprocatory movements to the tool While effecting a relative generating movement between the tool blank as though the gear being cut were meshing with the cylindrical gear described by the tool in its reciprocatory movement, the two tools used in cutting the two members of the gear pair having equal numbers of teeth.

11. The method of producing a pair of tapered cars which comprises generating each member I the pair conjugate to a cylindrical gear by ositicning a tool or cylindrical gear form having helically arranged cutting teeth in engagement with a tapered gear blank so that the axis of the tool is inclined to out offset from the axis of the blank, and imparting helical reciprocatory movements to the tool about and along its axis while effecting a relative generating movement between th tool and blank as though the gear being out were meshing with the helical gear described by the tool in its reciprocatory movements, the tools used in the cutting of the two members of the tapered gear pair being of opposite hand and being given helical reciprocatory movements of opposite hand.

12. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear other than its mate by positioning a rotary tool of cylindrical gear form having helically arranged cutting teeth in engagement with a tapered gear :lanls so that the axis of the tool is inclined to but offset from the axis of the blank, and imparting helical reciprocetory movements to the tool about and along its axis while effecting a relative generating motion between the tool and work as though the gear being out were meshing o ro with the helical gear desc bed by the tool in its, reciprocatoi'y pavements, ithe tools usea m't'uie; cutting O fith e twoihefnbers or the'tapereu ear pair being of 'o'pposite hanw-arid being given helical re'ciprocatory (movements T of opposite hand, and having, equal numbersof teeth. l3. 'I'hemethcd of. producing a pair of tapered gears which comprises generating each member ating movement betweenthetool and blank-as though the gear being cut were meshing with the cylindrical gear described by the tool in its reciprocating movement, the tools used in cutting the two members of the tapered gear pair having equal pitch diameters.

i i. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear by positioning a tool of cylindrical gear form in engagement with a tapered gear blank with the axis of the tool inclined to but offset from the axis of the blank, and imparting axial reciprocating movements to the tool while effecting a relative generating movement between the tool and blank as though the gear being out were meshing with the cylindrical gear described by the tool in its reciprocating movements, the two tools used in generating the two members of the tapered gear pair being of equal pitch diameter and having the same normal circular pitch.

15. The method of producing a pair of tapered gears which comprises generating each member of the pair by positioning a tool of cylindrical gear form having helically arranged cutting teeth in engagement with a tapered gear blank with the axis of the tool inclined to but offset from the axis of the blank, and imparting helical reciprocatory movements to the tool about and along its aXis while effecting a relative generating motion between the tool and blank as though the gear being out were meshing with the helical gear described by the tool in its reciprocating movements, the tools used in cutting the two members of the tapered gear pair being of opposite hand and being given helical reciprocating movements of opposite hand but of equal lead.

16. The method of producing a pair of tapered gears which comprises generating each member of the pair conjugate to a cylindrical gear other than its mate by positioning a rotary tool of cylindrical gear form having helically arranged cutting teeth in engagement with a tapered gear blank so that the axis of the tool is offset from but angular-1y inclined to the axis of the blank, and imparting helical reciprocating movements to the tool about and along its axis while effecting a relative generating motion between the tool and blank as though the gear being out were meshing with a cylindrical gear having teeth extending in the direction or" its axis and described by the tool in its reciprocating movements.

1?. In a machine for generating tapered gears, a base, a slide adjustable rectilinearly on the base, a cradle adjustable angularly on the slide, a work spindle iournaled in the cradle with its axis intersecting the axis of adjustment of the cradle, a tool support adjustable angularly on the base about an axis inclined to the axis of adjust- 19 ment of the cradle, a tool head mounted on the tool support, a, tool spindle journaled in the tool head with its axis inclined to and intersecting the axis of adjustment of the tool support and extending in the direction of the axis of adjustment of the slide, and a reciprocatory tool of cylindrical gear form secured to the tool spindle.

ERNEST WILDHABER.

REFERENCES CITED UNITED STATES PATENTS Name Date Wingqvist Jan. 11, 1921 Number Number Number 10 249,576 513,007 705,002

Name Date Fornaca, Nov. 2, 1926 'Irbojevich Aug. 25, 1931 Simmons Mar. 26, 1935 Miller Feb. 2, 1937 Miller Aug. 16, 1938 Miller Jan. 19, 1943 FOREIGN PATENTS Country Date Great Britain Mar. 25, 1926 Great Britain Oct. 2, 1939 Germany Apr. 22, 1941 

